Esterification - Sodium Carbonate or Sodium Hydrogen Carbonate (1 Viewer)

[pinkelephant]

We made an ester, and I'm now writing up my practical, and our method says that we used sodium carbonate solution, but everything i've read on esterification mentions sodium hydrogen carbonate solution.

What is the difference? Is my method wrong, or does sodium carbonate solution do the same thing?

Trust me not to read the label of what I was putting in it...

 

[Dreamerish*~]

Oh, we never used sodium carbonate solution.

Sodium bicarbonate or sodium hydrogen carbonate is baking soda. Its properties are very similar to that of sodium carbonate. I don't see why it makes a difference in esterification, because above temperatures of 60°C, it decomposes into sodium carbonate, water and carbon dioxide.

 

[Casmira]

doesnt the catalyst in esters accelerate the rate of reaction?

we used concetrated sulfuric acid because any water created is rapidly absorbed and since water is on products side, forward reaction is favoured D:

 

[Dreamerish*~]

doesnt the catalyst in esters accelerate the rate of reaction?

we used concetrated sulfuric acid because any water created is rapidly absorbed and since water is on products side, forward reaction is favoured D:

Sodium carbonate is not a catalyst. It's function is to remove traces of ethanoic acid and sulfuric acid that is still present in the distillate.

 

[Captain Gh3y]

Wait, what part of esterification needs sodium carbonate or sodium hydrogencarbonate to be used?

It couldn't be the catalyst because it's not an acid. Sodium hydrogencarbonate can be an acid, but would it even do what H2SO4 does as a catalyst in esterification?

Are you sure you're not getting confused with maybe calcium carbonate, which could be used for the boiling chips?

Google says sodium carbonate is used for isolating the ester, not sodium hydrogencarbonate, if that's what you meant.

AND: hsc online says that sodium hydrogen carbonate is used to neutralise any spills that may occur during the experiment.

 

[pinkelephant]

Well, we distilled the mixture of ester, ethanol and acetic acid, and because the temperature in the test tube only reached to around high 70s, in degrees celcius, it was possible that some ethanol passed over with the ester.

We used the sodium carbonate, or whatever it was, to separate the alcohol from the ester - I don't know how this happened.

The thing is - I think that it is because the water in the solution attracted the miscible ethanol, however I cannot find a reason for the sodium carbonate being used, because there isn't really any way that the acetic acid could be carried over with the distillate.

Unless ethanol is acidic - which I cannot work out, because I can't find any websites which will explain it, and I just keep hitting places which says that ethanol doesn't have a pH, but has a pKa (which I still don't understand).

 

[Casmira]

Sodium carbonate is not a catalyst. It's function is to remove traces of ethanoic acid and sulfuric acid that is still present in the distillate.

i dont have NaCO3 or NaHCO3 in my notes for ester set up ... =/ we never got mentioned it at all

 

[pinkelephant]

Yeah, our process is a bit weird in comparison to some of the others I have come across on this forum.

I don't see the purpose of the sodium carbonate either.

 

[pinkelephant]

Is there any use for the sodium carbonate???

I really need answers - this is frying my brains

I don't understand why there would be any sulfuric or acetic acid in the distillate.

 

[serge]

I don't understand why there would be any sulfuric or acetic acid in the distillate.

sulfuric acid's boiling point is much higher than what you use to distill the ester
so it will remain in the mix until you neutralise it

 

[standup]

No. there is no use for it to be blunt.
i wouldn't worry about it.. in an exam question on esterfication i reakon they will be looking for things like
reACTION CONDITIONS
-sulfuric acid - used as it speeds up the reaction AND absorbs water which moves the eualibrium to the right
-refluxing - heating in a vessel attached to a cooling condenser to avoid any volitile product or reactant to escape, allows reaction to occur at high temps.. (alcohol has lower b.p than alkonic acid as alkonic acid has strong H bonding (C=O) and extra polarity.)
-they might ask about boiling chips
USES...

i cant think wat else they would ask for in the exam

 

[pinkelephant]

Yerr, I know that stuff about the sulfuric acid (thanks anyways), but my problem was there was no real need (as far as I could see) to have the sodium carbonate, because the distilling temperature only really got as high as about 80 in the test tube, so I figured that the acetic acid wouldn't be carried over in the distillate, because of its high boiling point.

sulfuric acid's boiling point is much higher than what you use to distill the ester
so it will remain in the mix until you neutralise it

I knew that sufuric acid would never be carried over, coz the bp is like 337, so that was alright, but why would I need the sodium carbonate if there was no acetic acid? It shouldn't have evaporated coz its bp is around 118, and we only hit about 80

I just fudged some stuff about there being the possibility of having acetic acid evaporate, and that was the reason for it. I hope I don't fail.

I don't think that there'll be much on esterification in my exam, but i'm pretty much ready for anything that my teacher throws at us.

 

[serge]

I don't think that there'll be much on esterification in my exam, but i'm pretty much ready for anything that my teacher throws at us.

you have more school exams to do?

 

[Casmira]

our school just added abit of excess water to seperate the ester and acid, placed it in a seperating funnel, shook it and let the ester set on top and drain out water D:

 

[stargaze]

I wasn't aware of adding Sodium Carbonate into the ester mixture (at least in our prac at school we didnt)...

But take a look at a q19, Conquering Chemistry p181, it includes it in the Q... I was like wtf, thats this doing in there..

So it's function is to:

It's function is to remove traces of ethanoic acid and sulfuric acid that is still present in the distillate.

I'm not questioning that, but where did u find that out? And is that we need to know about Sodium carbonate?

 

[Casmira]

we had a question on describing the process on setting up how to make an ester and i never mentioned sodium carbonate, afaik wouldnt adding water react with sulfuric acid and any remainder ethanoic acid to form an aq mixture that doesnt react with ester at all ?

 

[jennylim]

yep, dreamerish is right. we learnt it and did it.

we did NaHCO3 solution.

the carbonate reacts with the acid to give salt, water and carbon dioxide. the CO2 bubbles off, the salt dissolves in the water and therefore the acid is gotten rid of through the separation funnel.

 

[Ghost1788]

i dont have NaCO3 or NaHCO3 in my notes for ester set up ... =/ we never got mentioned it at all

me 2

although wouldn't all the unreacted stuff end up in the organic layer when you are seperating the ester in the seperating funnel(i think thats what is called)..although it would be more efficient ie. better to make full use of the reactants...

 

[pinkelephant]

you have more school exams to do?

Yes!!! So stupid...

I'm a Canberran, so I've already done the ASTs, and we've just got ordinary school stuffs now. We finish in like 5 weeks or something. I've only got 2 exams, chem and maths. All my other classes are slack, and I don't have exams to them.

My chem one will be pretty easy, coz we've left all the easy stuff we had to cover, til this last semester. My maths one will be a cinch too, its just simple binomial probability.


To all peeps - thanks, I have just fudged some information, and it sounds seim-intelligent. i handed that prac report in today - its like the first assignment that i've finished more than a day before its due - i've handed it in 5 days before the due date - woot!!!

 

[wanton-wonton]

I haven't read all of that, but you have to use sodium carbonate. Na2CO3.